swift 学习笔记(23)-属性(计算属性)

//点

struct Point{
var x = 100
var y = 100
}
var point = Point()
print(point)

// 宽高
struct Size{
var width = 100
var height = 100
}
var size = Size()
print(size)

//区域
struct Rect{
var size = Size()
var origin = Point()

var center:Point{

// 只写 get 方法,就会是只读属性
get {
let x = rect.origin.x + rect.size.width/2
let y = rect.origin.y + rect.size.height/2
return Point(x: x , y: y )
}
//set 只是通过一种途径来修改属性的值
set(newValue) {

let x = newValue.x - size.width/2
let y = newValue.y - size.height/2
origin = Point(x: x, y:y)

}
}

}
var rect = Rect()
print(rect)

//求区域中心点

var p = Point(x: 100, y: 100)
var s = Size(width: 100, height: 100)
var r = Rect(size: s, origin: p)
print(r.center)
r.center = Point(x: 10, y: 10)
print(r.origin)